Pop your fuel cap and try the car next time out. You might have the tank vent line obstructed and after running for a time the lift pump is pulling against a fairly strong vaccum. Of course some degree of fuel starvation is happening at that point. Or if f you stopped the car when experiencing the power loss and removed the fuel cap a large intake whoosh would be heard if the tank vent is obstructed. Just a possibility and easy to check out. Easy is usually good. There are of course other possibilities as well.